Estoy tratando de instalar xlrd en mac 10.8.4 para poder leer archivos de Excel a través de python.

He seguido las instrucciones dehttp://www.simplistix.co.uk/presentations/python-excel.pdf

Hice esto:

descomprimido la carpeta al escritorio

en terminal, cd a la carpeta descomprimida

$ python setup.py install

Esto es lo que obtengo:

running install
running build
running build_py
creating build
creating build/lib
creating build/lib/xlrd
copying xlrd/__init__.py -> build/lib/xlrd
copying xlrd/biffh.py -> build/lib/xlrd
copying xlrd/book.py -> build/lib/xlrd
copying xlrd/compdoc.py -> build/lib/xlrd
copying xlrd/formatting.py -> build/lib/xlrd
copying xlrd/formula.py -> build/lib/xlrd
copying xlrd/info.py -> build/lib/xlrd
copying xlrd/licences.py -> build/lib/xlrd
copying xlrd/sheet.py -> build/lib/xlrd
copying xlrd/timemachine.py -> build/lib/xlrd
copying xlrd/xldate.py -> build/lib/xlrd
copying xlrd/xlsx.py -> build/lib/xlrd
creating build/lib/xlrd/doc
copying xlrd/doc/compdoc.html -> build/lib/xlrd/doc
copying xlrd/doc/xlrd.html -> build/lib/xlrd/doc
creating build/lib/xlrd/examples
copying xlrd/examples/namesdemo.xls -> build/lib/xlrd/examples
copying xlrd/examples/xlrdnameAPIdemo.py -> build/lib/xlrd/examples
running build_scripts
creating build/scripts-2.7
copying and adjusting scripts/runxlrd.py -> build/scripts-2.7
changing mode of build/scripts-2.7/runxlrd.py from 644 to 755
running install_lib
creating /Library/Python/2.7/site-packages/xlrd
error: could not create '/Library/Python/2.7/site-packages/xlrd': Permission denied

¿Por qué se niega el permiso? Gracias